Hello Erik,
To acheive the required, you can use a custom date attribute (e.g. adm-CustomAttributeDate1) and a scheduled task configured for the User object type. The custom date attribute will be used to specify the date when the account will be disabled. You can change the display name of the custom attribute to make it user friendly. The task condition will check whether the custom date attribute is before the current date/time. If the condition is met, the task will disable the user. The task configuration should look like this:
